Relatives of rubella virus in diverse mammals

We describe the first known relatives of rubella virus (Matonaviridae: Rubivirus)(1) in Africa and Europe. Ruhugu virus, the closest relative of rubella virus, was found in apparently healthy cyclops leaf-nosed bats (Hipposideros cyclops) in Uganda. Rustrela virus, outgroup to the rubella/ruhugu clade of viruses, was found in acutely encephalitic placental and marsupial animals at a zoo in Germany and in wild yellow-necked field mice (Apodemus flavicollis) at and near the zoo. Ruhugu and rustrela viruses share an identical genomic architecture with rubella virus(2,3). Amino acid sequences of rubella, ruhugu, and rustrela viruses are moderately to highly conserved within 4 putative B-cell epitopes in the fusion (EI) protein and, in the case of rubella and ruhugu viruses, within two putative T-cell epitopes in the capsid protein(4–6). Modeling of E1 homotrimers in the post-fusion state predicts similar host-cell membrane fusion capacity for ruhugu and rubella viruses(5). Together, these findings suggest show that some members of the Matonaviridae can cross wide host species barriers and that rubella virus likely had a zoonotic origin. Our findings raise concerns about future zoonotic transmission of rubella-like viruses but open doors for heretofore impossible comparative studies and novel animal models of rubella and congenital rubella syndrome.